I had a quick scan of the board before drying it and found the first issue. Looks like a SMD capacitor or resistor exploded. It's sitting right behind the PS2 and USB ports so either something got plugged into the board that was shorted or it has something to do with the PIII mod going wrong? Not sure how important this capacitor/resistor is at this stage.

The silkscreen say L7, so it's a small inductor or a ferrite for esd protection.

majinga wrote on 2026-06-10, 11:39:

The silkscreen say L7, so it's a small inductor or a ferrite for esd protection.

Thanks for that. I should have realised. It’s connected to the PS2 port so I don’t think it will prevent the board from posting. I can grind it down and repair it later.

Going to power on the board tomorrow with a thermal cam on it and see what happens. If nothing heats up like crazy or explodes, I’ll take some voltage measurements. Get your popcorn ready and sit back in your seats 🤣

Some high res images after the clean. She came out pretty good!

Well the board didn't explode after powering it on. All the temps from various chips look good. CPU gets warm. To rule out any BIOS chip or firmware issues, I installed a brand new BIOS chip and latest firmware from TRW.

Here are the voltages and clocks

Sadly, no post codes (tried 2 different celeron CPUs) BUT on one occasion when powering on the machine post code 05 appeared. So there is still some sort of life. This makes me think it's capacitors although I did run a ESR meter on all the caps and they checked out OK but you never know until you pull them completely out of the board.

It would be a lot easier if I had another board to compare voltages and resistances. Arrrg!

If anyone has any ideas on which direction to take, I'm all ears.

https://www.alldatasheetru.com/datasheet-pdf/ … MI/CS51313.html
For some reason, the voltage varies between the different CPUs – 2V and 1.3V.
Without the CPU, the CS51313 PWM should output 1.25V (All VID=1)

zuldan wrote on 2026-06-11, 07:47:

Well the board didn't explode after powering it on. All the temps from various chips look good. CPU gets warm. To rule out any […]
Show full quote

Well the board didn't explode after powering it on. All the temps from various chips look good. CPU gets warm. To rule out any BIOS chip or firmware issues, I installed a brand new BIOS chip and latest firmware from TRW.

Here are the voltages and clocks

The attachment BP6 - Front - Voltages.png is no longer available

Sadly, no post codes (tried 2 different celeron CPUs) BUT on one occasion when powering on the machine post code 05 appeared. So there is still some sort of life. This makes me think it's capacitors although I did run a ESR meter on all the caps and they checked out OK but you never know until you pull them completely out of the board.

The attachment POST.JPG is no longer available

It would be a lot easier if I had another board to compare voltages and resistances. Arrrg!

If anyone has any ideas on which direction to take, I'm all ears.

Hi,

As I'm not familiar with this exact model of motherboard these are only ideas based on what I experienced with other MBs:

1. This is a dual CPU MB, Intel didn't really liked Celerons running in dual CPU configurations, so it is possible that it will not boot with Celerons.
2. Some motherboards don't like it if a Memory Slot is populated without the first memory slot also being populated, according to the manual there(https://theretroweb.com/motherboard/manual/bp … f0584560285.pdf), the first slot is the one closest to the CPUs on this motherboard, while your image shows the module in the farthest slot. (This however most often results in beeps coming from the speaker)
3. If you tried the two CPUs separately and not together and put them into the same socket, some motherboards have a primary socket that needs the CPU installed and doesn't work properly with the CPU only present in the secondary socket. (Although the manual seems to imply that there are no primary CPUs on this MB, if only trying with a single CPU, I would try it with the CPU in the socket marked as CPU1 in the manual.
4. In the first picture the BIOS battery seems to be missing, and I cannot see it in the second picture, if you put in a battery between the two pictures ignore this comment, but without a BIOS battery many motherboards cannot even POST properly.

That is all that is currently coming to mind, but I will check back on this topic.

EDIT: Most likely you can ignore my 2nd suggestion, now rereading the manual I can see that they mention that the slots can be populated in any order.(If I have only a single memory stick I would still place it into the 1st slot though)

shevalier wrote on 2026-06-11, 08:18:

https://www.alldatasheetru.com/datasheet-pdf/ … MI/CS51313.html
For some reason, the voltage varies between the different CPUs – 2V and 1.3V.
Without the CPU, the CS51313 PWM should output 1.25V (All VID=1)

VOUT is 2.0v on the top CS51313 chip with the CPU installed on the left socket
VOUT is 1.3v on the bottom CS51313 chip with the right socket empty

VOUT is 1.3v on the bottom CS51313 chip with the left socket empty
VOUT is 2.0v on the top CS51313 chip with the CPU installed on the right socket

So the CS51313 chips appear to be working

MagefromAntares wrote on 2026-06-11, 08:24:

1. This is a dual CPU MB, Intel didn't really liked Celerons running in dual CPU configurations, so it is possible that it will […]
Show full quote

1. This is a dual CPU MB, Intel didn't really liked Celerons running in dual CPU configurations, so it is possible that it will not boot with Celerons.
2. Some motherboards don't like it if a Memory Slot is populated without the first memory slot also being populated, according to the manual there(https://theretroweb.com/motherboard/manual/bp … f0584560285.pdf), the first slot is the one closest to the CPUs on this motherboard, while your image shows the module in the farthest slot. (This however most often results in beeps coming from the speaker)
3. If you tried the two CPUs separately and not together and put them into the same socket, some motherboards have a primary socket that needs the CPU installed and doesn't work properly with the CPU only present in the secondary socket. (Although the manual seems to imply that there are no primary CPUs on this MB, if only trying with a single CPU, I would try it with the CPU in the socket marked as CPU1 in the manual.
4. In the first picture the BIOS battery seems to be missing, and I cannot see it in the second picture, if you put in a battery between the two pictures ignore this comment, but without a BIOS battery many motherboards cannot even POST properly.

1. This motherboard only accepts Celerons unless it's modified for P3
2. Tried with memory populated and unpopulated
3. I've tried both CPU sockets, with 1 CPU in at a time
4. I've with a battery and without

I don't think a BX motherboard puts out any POST information on PCI. Could you try your reader in an ISA slot? Take careful note of which orientation you install it, though. Pretty sure it's marked somehow (mine has "back" or "rear" written with an arrow to which side must point backwards (towards the pcb edge)

H3nrik V! wrote on 2026-06-13, 05:59:

I don't think a BX motherboard puts out any POST information on PCI. Could you try your reader in an ISA slot? Take careful note of which orientation you install it, though. Pretty sure it's marked somehow (mine has "back" or "rear" written with an arrow to which side must point backwards (towards the pcb edge)

I think I've tried the post card in the ISA slot. Will check again to be 100% sure. I've done a full recap, found 5 bad caps. But the motherboard still does not post. I think next to is to see if the BIOS chip is talking to the CPU.

zuldan wrote on 2026-06-13, 06:12:

H3nrik V! wrote on 2026-06-13, 05:59:

I don't think a BX motherboard puts out any POST information on PCI. Could you try your reader in an ISA slot? Take careful note of which orientation you install it, though. Pretty sure it's marked somehow (mine has "back" or "rear" written with an arrow to which side must point backwards (towards the pcb edge)

I think I've tried the post card in the ISA slot. Will check again to be 100% sure. I've done a full recap, found 5 bad caps. But the motherboard still does not post. I think next to is to see if the BIOS chip is talking to the CPU.

FWIV, that card looks exactly like mine, and mine shows nothing anymore - even on a working board 🤷‍♂️

If you connect the speaker to the motherboard, does it produce any sound?

And does the RESET LED on the POST card respond when pressed key?

I would also try to dip it in a ultrasonic bath for the cpu-sockets.
Soot sticks easily and needs some agitation to remove. Also, it's conductive, and depending on the fire it was in, it can be very corrosive.

You see any modification to the board?
If I remember correctly, the only way to use a P3 on this board is with a Powerleap NEO s370, or by some mods.

H3nrik V! wrote on 2026-06-13, 05:59:

I don't think a BX motherboard puts out any POST information on PCI. Could you try your reader in an ISA slot? Take careful note of which orientation you install it, though. Pretty sure it's marked somehow (mine has "back" or "rear" written with an arrow to which side must point backwards (towards the pcb edge)

They do, in fact I've had more luck getting POST codes over PCI than ISA with them 🤣

H3nrik V! wrote on 2026-06-13, 06:21:

FWIV, that card looks exactly like mine, and mine shows nothing anymore - even on a working board 🤷‍♂️

These cards die after a while. I buy a few at a time 😉

shevalier wrote on 2026-06-13, 07:01:

If you connect the speaker to the motherboard, does it produce any sound?

And does the RESET LED on the POST card respond when pressed key?

PC Speaker produces no sound. I'd prefer not to plug in the PS2 keyboard yet until I've sorted out that part of the board that had a burn mark 😉 Thanks for the suggestion though.

oh2ftu wrote on 2026-06-13, 14:25:

I would also try to dip it in a ultrasonic bath for the cpu-sockets.
Soot sticks easily and needs some agitation to remove. Also, it's conductive, and depending on the fire it was in, it can be very corrosive.

This is a good idea. Let me do a little more diagnosing and don't get anywhere, I'll try this.